The biggest long-term threat to the iPhone isn’t Android, Samsung Electronics Co. or China’s bevy of cheap phone makers. Instead, it’s a deceptively simple idea: Apps work better if you embed them in a single program, rather than let them proliferate across your home screen. WeChat, China’s leading social media app, just launched a new platform with exactly that idea in mind. It has the potential to reconfigure smartphones as radically as anything since the first iPhone was released.

The company calls the concept “mini programs,” and the idea is that users can call up useful features from third parties — photo filters, language tools, ride-sharing services — within the WeChat app and use them instantly, with no downloading or installation required. Although that sounds like a modest innovation, it solves two crucial problems plaguing the app model.

First, the average size of an app has been increasing as developers pack in more features and media to take advantage of better screens and hardware. That’s not a problem if you have unlimited data and a brand new iPhone 7. But in emerging markets, where smartphone use is growing quickly, consumers tend to use capped data plans and older phone models with less memory. So big apps aren’t just inconvenient — they’re less likely to be downloaded in the first place.

The second problem is one shared by users worldwide: Registering an app is annoying. E-commerce apps, in particular, require usernames, passwords, payment information and e-mail addresses before they’ll work. Inputting all that is aggravating on a small screen, and worrisome at a time when identity theft is rising (especially in China). And how often do you really use that pizza-ordering app that holds all your personal info?

Mini programs, by contrast, aren’t found in an app store. Users get links to them from friends or groups in a chat, or by scanning a QR code in real life (at a restaurant, say). Because they operate from the cloud, there’s no bandwidth-eating downloads. Because they accept payments from WeChat’s wallet, there’s no need to register or divulge payment information. Even better, on Android the mini programs can be pinned to the home screen. They work just like regular apps, in other words, only without all the hassle.

WeChat isn’t the only service to experiment with mini programs, but it’s better positioned than any other to succeed. For one thing, it has 768 million daily users, half of whom spend at least 90 minutes per day on the service. It’s increasingly synonymous with the internet in China: Drop into a subway train and everyone you see is using it.

Those users aren’t just chatting or sharing vacation photos with friends. They’re also interacting with “official accounts” run by companies, which appear in a user’s timeline and push news and merchandise. WeChat facilitates payments made to those accounts through its wallet. (Unlike with Apple Pay, it doesn’t require a phone with a fingerprint reader.) Users get access to promotions, products, services and even tools to pay their utility bills, all in a format that makes commerce an inherently social activity. That convenience, in turn, makes WeChat a powerful shopping destination — even a lifestyle — which keeps users in the ecosystem.

WeChat had already morphed beyond its roots as a chat service to become a one-stop app for everything, from banking to shopping to dating to dining. With each new feature and service it adds, users have fewer and fewer reasons to leave it, or to download other apps. Mini programs may eliminate the need altogether.

In short, WeChat is starting to look quite a bit like a mobile operating system. As it becomes more powerful and self-contained, Chinese phone consumers will stop asking what phone and operating system they should buy, and start contemplating what phone best runs WeChat. That’s a long-term threat to iOS and Android, as well as any company that makes phones to run them.

Apple Inc. isn’t taking this development lightly. It even prohibited WeChat from using the term “app” as applied to mini programs. But the challenge to the App Store might be the least of Apple’s worries. For now, WeChat is changing smartphones in China. One day soon, its impact will be felt worldwide.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.